It looks like the roads will be closed around the time I was planning on being there, very unfortunate as it's a big part of the trip. Looks like I'm going to have to re arrange the Swiss part another time ,and take advantage of the amazing views and roads around later in the year.

Would you say that July would have good weather usually on the mountain passes ?

And certainly I will coming back to this forum for advice when it comes to the next trip , very informative and quick responding replies which is very greatly appreciated.

Well, they may be closed, but could be open as well. You need to have an alternative route in mind if you come in May. July through September are perfect. All passes will be open, except of course for the unpredictable: snow storms and landslides can occur at any time at that altitude.

If you go to the downloads link on the above site, you can download a PDF showing opening and closing times of the passes for the last 20 years or so. That shows that the Furka and Grimsel passes have only been open by 24 May in 4 or 5 years out of the last 22 years, so the chances don't look good!